I just started using Brewer's Friend. (I was previously using BeerSmith and BrewTarget.) I like that the software web-based, so I can reference it at homebrew club meetings or brew sessions at a friend's house.

Features:

Recipe calculator including expected OG and FG, IBUs, SRM color, and other common measures of a beer. (This includes multiple formulas/methods for calculating each.)

Recipe scaling.

Water conditioning calculator for areas with regionally variable water supplies.

Unit conversions between imperial and metric (temp, volume, etc) are a little clunky.

No mobile phone interface.

Advantages:

Portable. Create a recipe at work, view it at home, brew it at a friend's house.

Under active development. New features seem to come around frequently.

Disclaimer: I'm a web developer who found this homebrew site through some of the web development siblings on the Stack Exchange network. I appreciate that Brewer's Friend is a small start-up site under active development and that probably colors my view.

I found an iPhone/iPod Touch app called Brew Pal that has been really great. It is very convenient to be able to carry in my pocket and also take with me if I am brewing at a friends house. The timers and calculators have been very helpful to me.

I've used Brew Pal and can't fully recommend it. It can give you really weird gravity estimates. I've tried contacting the author with some bug reports and have never heard back.
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HopwiseJan 13 '11 at 16:51

If you have an iPhone, there's a $1 app called Brew Pal. It works great for sparge calculations (strike temp and volume), grain bill, hop schedule. You can even calculate the efficiency of your brew system. You can also email the recipe to yourself after you've entered it all into the app. Its great, and portable.
-Bryan

Used promash for a few years, then beersmith, both through a windows emulator (on a mac). Currently BeerToolsPro, very happy with it especially since its a native mac program, also available for windows. Able to open .xml and .rec files too.

I used a few of the online systems (Hopville, then BrewToad, etc.) until I got tired of the interfaces - I thought they were cumbersome and inefficient, and I had no idea how they were doing their calculations. So I created my own Excel document, with numerous tabs, that I use for several things - recipe development, stock on hand (hops in storage, etc.), all my costs (equipment & ingredients), tasting notes, etc., etc. ... I can also print out recipes, notes, and schedules, and if I don't like the way something is set-up, I can change it. It took me a while to find the necessary formulas for everything I wanted to do, and to develop my own spreadsheets for calculating IBUs and whatnot, but I learned a TON in the process, and now I'm free from depending on someone else's ideas for what the software/interface should be, not to mention the cost. I know not everyone is inclined to do something like this on his/her own, or has the knowledge (though I'm no Excel whiz, either) ... but if you ARE inclined - and I think it's safe to say that a lot of us homebrewers are, by nature, DIY-types - I strongly recommend learning what you can from other softwares, gathering and understanding the relevant formulas, and then developing your own system using some sort of spreadsheet program. Just start chipping away at it, and in a few months you'll have a fairly robust system that you can always tweak and improve. Cheers!

I've had it up to here with BeerSmith2 in that it's backwards (you enter an efficiency and it forces that down, instead of entering the data and calculating the efficiency). What spreadsheet do you use?
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DaleJan 18 '12 at 23:40

There is also Strange Brew (strangebrew.ca). I've used it for about 8 years now and it does everything I've needed it to do. You can download a trial version or there is also a free Java version (with less features) available on sourceforge.

The author of it also has a hilarious random beer name generator on his site, check it out.